1. Field of the Invention
The present invention relates to a gene for an A-type inclusion body (ATI) of poxvirus. More specifically, it relates to a structural gene coding for a major protein of A-type inclusion body and a promoter necessary for the expression of the structural gene.
2. Description of the Related Art
Vaccines currently used include attenuated vaccines using attenuated living viruses or bacteria and inactivated vaccines using inactivated viruses or bacteria.
The attenuated vaccines have advantages in that they induce not only a humoral immune response but also a cell-mediated immune response, which responses are relatively high and can be produced at a low cost. However, sometimes side effects although occur even though these vaccines are attenuated. Moreover, there are various pathogens which have not been attenuated, and therefore, the attenuated vaccines are not universal for all kinds of pathogens.
On the other hand, although inactivated vaccines are relatively safe, they are disadvantageous in that they have a lower effectiveness.
In contrast with these conventional vaccines, new types of vaccines involving gene recombination technology are now under development. According to one of these techniques, an antigen gene of a pathogen is introduced to a plasmid, which is then used to transform bacterium such as Escherichia coli or yeast. The resulting transformant is then cultured to produce a large amount of an antigen protein, which is then recovered and purified to produce a vaccine. In this technique, once a small amount of antigen gene is obtained, it becomes easy to produce a large amount of vaccine which is not pathogenic. However, some problems relating to purifying method of the antigen protein, the selecting of an adjuvant used for the antigen protein, and the like, are yet unsolved. In another technique involving gene recombination technology, an antigen gene derived from a pathogen is introduced to an nonessential region of a vaccinia virus gene to construct a recombinant vaccinia virus containing the exogeneous gene, and the recombinant virus is used as a live vaccine. These vaccines essentially fall under the category of conventional live vaccines, and therefore, possess the advantages of the conventional live vaccine. Moreover, according to this technique, the use of an attenuated vaccinia virus as a vector provides safe vaccines with a low toxicity. In addition, this technique is universal in that a vaccine against any kind of pathogen can be produced. This advantage is not found in conventional vaccines.
According to a typical procedure of this technique, a gene coding an antigen protein of interest (antigen gene) is separated from a pathogen in question, and the antigen gene is cloned in a conventional E. coli plasmid. On the other hand, a nonessential region of gene of vaccinia virus or related virus is separated, and the nonessential region is introduced to an appropriate plasmid such as E. coli plasmid. The above-mentioned antigen gene is then inserted into the nonessential region of the plasmid to construct a recombinant plasmid, and next, the nonessential gene region of the virus origin interrupted with the antigen gene is recombined with a corresponding region of a gene of the vaccinia virus as a vector, to construct a recombinant vaccinia virus having a gene containing the target antigen gene. If the recombinant virus injected to a host such as a human or other animal can express the exogeneous antigen gene in an amount sufficient to generate an immune response in the host, the recombinant virus can be used as an attenuated vaccine.
Note, since the attenuation of a virus and the generation of an immune response are mutually exclusive phenomena, serious efforts are being made to develop a strong virus promoter which can sufficiently express an exogeneous gene in an attenuated virus.